Concrete is the most consumed man-made material in the world. A typical concrete is made by mixing Portland cement, water and aggregates such as sand and crushed stone. Portland cement is a synthetic material made by burning a mixture of ground limestone and clay, or materials of similar composition in a rotary kiln at a sintering temperature of 1450° C. Portland cement manufacturing is not only an energy-intensive process, but one which releases considerable quantities of greenhouse gas (CO2). The cement industry accounts for approximately 5% of global anthropogenic CO2 emissions. More than 60% of this CO2 comes from the chemical decomposition, or calcination of limestone.
There has been growing effort to reduce total CO2 emissions within the cement industry. According to a proposal by the International Energy Agency, the cement industry needs to reduce its CO2 emissions from 2.0 Gt in 2007 to 1.55 Gt by 2050. This represents a daunting task because, over this same period, cement production is projected to grow from 2.6 Gt to 4.4 Gt.
To meet this formidable challenge, a revolutionary approach to cement production was developed that significantly reduces the energy requirement and CO2 emissions of a cement plant. The unique cement is comprised of carbonatable calcium silicate compositions and is made from widely available, low cost raw materials and offers the ability to permanently and safely sequester CO2 while being adaptable and flexible in equipment and production requirements, allowing manufacturers of conventional cement to easily convert to the new platform.
“Clinker” refers to lumps or nodules produced by heating in a rotary kiln at high temperature a mixture of raw materials including limestone and alumino-silicate materials such as clay (˜1,450° C. in Portland cement). Cement clinker is ground to a fine powder for use in many cement products.
Besides reactivity, clinker grindability is an important measure of the clinker quality. Considerable energy is consumed at a cement plant for clinker grinding. Improved clinker grindability thus increases grinding efficiency and reduces energy consumption. For the carbonatable calcium silicate-based cement production, clinker grindability is an important property. Unlike in the case of Portland cement, grindability of calcium silicate-based clinker is not understood nor is grindability optimization achieved.
Thus, it is important to develop suitable clinker production methodologies that yield favored clinker microstructures and desired grindability profile and reactivity.